Question

Monochromatic light (that is, light of a single wavelength) is to be absorbed by a sheet of photographic film

and thus recorded on the film. Photon absorption will occur if the photon energy equals or exceeds 0.6 eV,

the smallest amount of energy needed to dissociate an AgBr molecule in the film.

(a) What is the greatest wavelength of light that can be recorded by the film? (5 marks)

(b) In what region of the electromagnetic spectrum is this wavelength located?​

Answer 1

a) the smallest amount of the energy that is dissociat the AgBr molecule in the film is 0.6eV, the energy of photon equal the frequency of the photon multiplied by the planck's constant that is

E=hf

the frequency is given by

f= c/lambda

thus

E = hc/ lambda

solve lambda to get

lambda = hc/E

to find the corresponding wavelength for the energy 0.6eV we subsitute into the above equation , (note that planks constant in eV unit is h= 4.136×10^-15 eV ) to get it

lambda = (4.136^-15 eV.s)(3.0 × 10^8 m/s)÷ o.6ev

= 2.1× 10 ^-6 m